Minn. R. Part 7050.0227
The numeric and narrative water quality standards in this part prescribe the qualities or properties of the waters of the state that have limited resource value designated public uses and benefits. If the standards in this part are exceeded in waters of the state that have the Class 7 designation, it is considered indicative of a polluted condition which is actually or potentially deleterious, harmful, detrimental, or injurious with respect to the designated uses.
The quality of Class 7 waters of the state shall be such as to protect aesthetic qualities, secondary body contact use, and groundwater for use as a potable water supply. Standards for substances, characteristics, or pollutants given below shall not be exceeded in the waters:
| Substance, Characteristic, or Pollutant | Class 7 Standard |
| Escherichia (E.) coli | Not to exceed 630 organisms per 100 milliliters as a geometric mean of not less than five samples representative of conditions within any calendar month, nor shall more than ten percent of all samples taken during any calendar month individually exceed 1,260 organisms per 100 milliliters. The standard applies only between May 1 and October 31. |
| Oxygen, dissolved | The level of dissolved oxygen must be maintained at concentrations: |
| i. that will avoid odors or putrid conditions in the receiving water;. | |
| ii. at not less than 1 mg/L (daily average); and | |
| iii. above 0 mg/L at all times. | |
| pH, minimum value | 6.0 |
| pH, maximum value | 9.0 |
| Toxic pollutants | Toxic pollutants shall not be allowed in such quantities or concentrations that will impair the specified uses. |
Minn. R. Part 7050.0227
Statutory Authority: MS s 115.03; 115.44